 	(/ (- (square (Math/sin phi_0))
 	      (square (Math/sin phi_n_i)))
 	   (square (double (second n_i))))))))
+
 
 ;; Overall Energy and Force
 

	       :when (and (order [n_i v_1])
			  (not (order [n_i v_2])))]
	   (- (nth (pos v_1) part) (nth (pos v_2) part))))))

;; Gravitative Energy and Force


    (* (/ (square (node-line-distance (node-positions v)
				      [(node-positions x), (node-positions y)])))
       (node-line-distance-derivative v [x y] n_i part (:lattice information)))))


;; Attractive Energy and Force

